Cutter chain



Patented June 3, 1941 UNITED STATES PATENT OFFICE CUTTER CII-AIN Massachusetts Application Februaryli, 1933, Serial No. 658,804

(cl. 2oz-s3) v 24 Claims. This invention relates to cutter chains, and

more particularly to improvements in cutter chains especially'designed for use with coal cutting machines.

An object of this invention is tov provide animproved cutter chain. Another object is to provide an improved cutter chain having embodied therein improved means for holding the cutter bit in place with respect to the bit block. Still another object is to provide an improved cutter bit holder. A further object is to provide acutter bit having a pair of cutting ends and having associated therewith improved holding means therefor for holding the same in position upon the cutter chain. Still another object is to provide an improved mounting for a cutter bit which clamps the same i'lrmly in position, a'nd through the cooperation withl the bit of means providing an abutment limiting rearward movement of the bit and means for moving a bit supporting element, effects a/tght holding of the bit, and a placing of the same actually under longitudinal compression. A further object of the invention is to provide an improved cutter bit and mounting combination including improved means for releasing a bit fordorward withdrawal from its holder and for selectively holding it securely under longitudinal pressure applied through the action of a set screw in a chain block upon a bit holder. Still a further object is to provide an improved bit holding means including a holder element and an abutment coacting with the active cutting face of the bit towards and from engagement with which abutment the bit is moved by movement of the holder in and out in a holder-receiving socket arranged in the usual angular relation to a chain block. These and other objects of the invention will, however, hereinafter more fully appear'in the course of the ensuing description and as more particularly pointed out in the appended claims.

In the accompanying drawing there are shown for purposes of illustration two forms which the invention may assume in practice.

In this drawing- Fig. -l is a side elevational view of the preferred illustrative embodiment of the improved cutter chain.

Fig. 6 is a perspective view of the bit holder. Fig. 7 is a perspective view of the element.

Fig. 8 is a fragmentary view similar to Fig. 3, showing a modined form of construction.

Fig. 9 is a perspective view of the bit holder shown in Fig. 8.

In both-l of the illustrative constructions both the cutter bit and bit holding means are shown associated with a cutter chain ot essentially a standard design comprising a bit block or chain link I pivotally connected at 2 to side straps 3. The bit block and side straps have lateral guiding portions 4 and 5, respectively, and the block and straps cooperate to form an inner guiding surface 6. The bit block has a projecting head or lug traversed by a socket 'I arranged at right angles to the maior axis of the bit block and perpendicular to the inner guiding surface 6 of the chain. The front wall of the blt holder is perforated by a threaded opening 8 for reeciving a special set screw 9 to hold the bit holder structure in .position within the bit block socket. It will be evident, however, that the improved bit and bit holding means arrangement may be used, with or without minor imodication, in cutter chains of various other types, and it is therefore not desired to limit the invention to the particular type of cutter chain shown. 4

Now referring to the improved bit and bit hold.- ing means arrangement, it will be noted that projecting within the bit block socket] is the solid shank or body I0 of a bit holding and clamping member I I having a head formed with a socket I2 for receiving a plural armed orl double pointed cutter bit I3. 'I'he bit holder shank III is provided with laterally projecting convex sides Il iltting within concave grooves I5 formed longitudinally of the opposite side walls o1' the bit block socket, as shown in Fig. 4. Also having a rectangular portion I6 projecting within the chain block socket and abutting theforward tace of the bit holder shank is la block element or abutment element I'I, this element having a forwardly projecting rectangular portion I8- underlying the' forward portion of the bit body and arranged with its inner surface I9 engaging the Fig. 2 is a transverse vertical sectional view taken substantially on line 2-2 of Fig. 1.

Fig. 3 is a central longitudinal sectional view taken substantially on line 3-3 of Fig. 2.

Fig. 4 is a detail sectional view taken on line I-I of Fig. 3.

outer surface of the bit block. The element I1 is positioned and guided within a recess 20 formed by parallel projections 2l, 2| at thevsides of the bit holder, as shown. In this instance, the bit holder has an inclined surface 22 cut in its Iorward face adjacent the inner end of its shank for engagement with the tapered or conical end 23' of the set screw 9, the inclined surfaces-on the abutment v its longitudinal axis l element I1, and when a above described, but

bit holder and set screw, when the latter is tightened, clamping the bit holder and the element I1 in bit holding position within the bit block socket with a wedging action, and as a result clamping the bit under longitudinal or endwise compression rigidly relative to the bit block.

The cutter bit per se is inthe form of a cylindrical rod section herein composed of bar stock having beveled end surfaces 24 and 25 forming cutting points 26 at the opposite ends of the cylindrical bit body. The bit may be formed from various symmetrically shaped bar stocks, the cutting faces being formed by cutting the stock diagonally, and the stock being turned 180 about between each pair of cuts. By selecting bar stock which'is of symmetrical form with respect to axes at right angles to each other, the faces of each bit will necessarily 1be identic, if the angle of the cutter to the barbe maintained the same. After being formed the bit will be hardened and tempered as may be desired, and will require no individual sharpening if suitable bar stock be employed. The finished 'bit has its points 26, 26 at its opposite ends, and

at the extremities of elongated faces which are identic in outline and lie in planes forming an obtuse dihedral angle, and are individually symmetrical as to both major and minor axial lines. Again referring to the bit holding means, it will be noted that the socket in the bit holder is circular in cro'ss section to receive the cylindrical bit body, and the element I1 has a concave seat 21 within which the lower forward portion of the bit body rests, and the forward end of the abutment element I1 is upset to provide a plane surface 2B abutting the inner portion of the inclined surface 24 of the bit and against which the latter rests in the manner shown in Fig. 3. The cutter bit is of the reversible type so that when the active point of the cutter bit becomes dull, the parts may be loosened within the bit block socket and the bit turned end for end within the bit holder socket, thereby to present a new cutting point, the inclined surface 24 of the bit at that time engaging the outer surface of the bit block, while the inclined surface 28 on the element I1 then engages the inclined surface of the bit.

The bit may obviously be reversed or replaced in various ways. For example, the holder I I, the abutment element I1 and the bit may-be removed from the chain block, moved relative to the reversal or replacement of the bit may be effected, the parts moved to bit holding position, and the holder and abutment element returned 'to the socket 1 with the bit positioned between them; or, as another illustrative way, while the element I1 remains stationary on the chain block the holder I I, released from clamping by the set screw 9, may be slid outwardly far enough to permit withdrawal of the bit over the top of the bit change has been effected, be pushed inward once more and engaged and moved by the set screw to effect bit clamping.

In the modied form of construction shown in Figs. 8 and 9, the cutter bit I3 is identical to that in this instance the abutment element I1 is formed integral with the bit holder and the bit holder shank is heldin position within the bit block socket 1 by means of a standard set screw 30 abutting the forward face of the bit holder shank. In this form of the invention, the bit holder shank is designated 3l and the bit holder, 32. Formed in the head of 'the bit holder is a cylindrical socket 33 for receiving the the abutment element be holder to release the bit,

bit body, and the bit holder has a forwardly projecting portion 34 underlying the forward portion of the bit body and having an upset end 35 formed with an inclined surface 36 engaging the inclined surface 24 on the bit and against which the latter rests. As in the form above described, the inclined surface 25 on the bit, when the parts are in the position shown, engages the' outer surface of the bit block. When the bit point becomes dull the bit holder is released from the bit block socket and the bit withdrawn axially rearwardly from the bit holder socket, turned end for end, and then re-inserted in the bit holder, and the latter is thereafter inserted within the bit block socket and secured therein. Otherwise this form of the invention is the same as that described above.

As a result of this invention, it will be noted that an improvedl cutter chain is provided having a cutter bit andimproved and novel holding means engageable with the bit for holding the bit in place upon the block. It will further be noted that the cutter bit is provided which may be used with a cutter chain of a standard design and may be readily and cheaply formed, the cutter bit being of a simple design and having associated therewith holding means of an extremely simple character. It will also be noted that an improved of the active cutting face of the bit in securing the bit firmly in position during cutting. It will likewise be observed that improved means for forcing the holder inwardly into its socket and for clamping the bit under longitudinal compression are provided. Moreover, it will be observed that through the provision of a seating surface adjacent the forward side of the holder for seating the outer oblique end face of the cutter bit, the latter will be most effectively prevented from escape during use. Moreover, through the provisionl of 'an abutment on the block having an abutment surface engageable with a portion of the active cutting surface of the bit, and through improved bit-positioning and "holding means, a firm holding of the bit will be attained. It will further be noted that upon the release of the set screw' 9, upward movement of the holder element Il relative to the abutment element I1 may be effected while the latter element remains stationary, to a degree suicient to free the bit I3 for forward withdrawal without a complete removal of the parts received in the socket 1 from the latter. Accordingly, bit release can be effected by longitudinal movement of the element II relative to the element I1 in one direction and bit clamping effected by the opposite relative movement of the holder element II. These and other uses and advantages of the improved'cutter chain will be clearly apparent to those skilled in the art. l

While there are in this application specifically described two forms which the invention may assume in-practice, it will be understood that these forms of the same are shown for purposes of illustration and that the invention may be modified and embodied in various other forms without departing from its spirit or the scope of the appended claims. y

What I claim as new and desire to secure by Letters Patent is:

1. A cutter bit holder having a shank and a holder portion having an opening for receiving and surrounding a cutter bit, said opening inclined forwardly and outwardly for and receiving the body ofa cutter bit, and an integral front holder having a bit receiving bore obliquely dis-v posed downwardly through the head thereof, a cutter tooth having opposingly diagonally cut ends providing sharp points at the same sideof the tooth, said cutter tooth mounted in said head bore with one end resting on the block.

3. In a cutter chain having links adapted to shank, a plural armed bit seated in a recess in the head with an arm projecting outwardly therefrom in position to cut, and means movable in the holder in a plane substantially at right angles to the plane of cutter chain travel and cooperating with the projecting arm to prevent displacement of the bit from its recess.

4. A mining chain link, a bit holder attached to the link, a bit seated in a recess in the holder, and a member slidable in the holder in a plane at a substantial angle to the plane of chain travel and cooperable with the link when said holder is seated in said link to block the exit of the bit from the recess in the holder.

' 5. In a cutter chain, a chain block having a socket, a double-pointed reversible cutterbit having cutting faces at its opposite ends, an element support bits, a bit holder having a head and a' mounted on said chain block and having an inclined surface engageable with the inner end of the active cutting face of the bit when the latter is mounted in cutting position relative to said block, a bit holder receivable in said block socket and having an inclined bit-receiving socket for receiving said cutter bit, said bit holder movable providing element remains mounted on the block in stationary relation' with respect to the latter, to move the bit out of contact with said inclined surface and to free the bit for withdrawal forwardly past said element, and means secured `within said chain block and engageable with said holder for moving the latter relatively to the block socket and to said inclined surface to effect bit clamping,` said inclined surface of said element causing the bit to be pressed inwardly within the holder socket as said holder is so moved relatively to the chain block socket.

6. In a cutter chain, in combination, a socketproviding, cutter-supporting chain block, a -dou-f ble-ended bit' provided with cutting surfaces at its opposite ends each symmetrical with respect both to major and minor axes land respectively lying in the sides of an obtuse dihedral angle, and means for supporting said bit upon said block including a bit holder having a shank receivablel within said block socket and a head provided with l downwardly rearwardly inclined bit-receiving opening extending therethrough, means acting on said shank to press the same rearwardly in said socket, and an element having a portion receivable within the chain block and another portion providing an abutment surface engageable ,with an inactive portion of the active cutting end of the bit when the latter isin cutting position on said chain block, said bit holder positionable relative to said element, while said element remains stationary with respect to said block with its portion so receivable received within the block and while the bit holder shank remains at least in part within said block socket, alternatively to release the bit for withdrawal, from said bit-receiving opening or to clamp the same against said abutment surface.

7. A bit carrying lug for a mining machine chain including a socket having a forward wall, a holder mounted in said socket, said holder including a cutter bit receiving opening, a cutter bit mounted in said opening with an end thereof extended angularly forwardly from the holder, and

an abutment disposed on said lug forwardly of and projecting outwardly with respect to the forward wall of said socket, said cutter bit having its extended end in engagement with said abutment when disposed in cutting position on said lug and said holder reciprocable in said socket relative to said abutment and upon one direci 8. In a mining machine chain, a chain ,link

including a lug portion, said lug portion including a socket at least approximately at-right angles to the length of the link, a holder mounted in said socket, a double ended-cutter bit mounted in the outer end ofv said holder and projecting angularly forwardly' therefrom, a clamping device for forcing said holder inwardly in its socket for binding the bit in its holder by the engagement of one end of the bit in end abutment with the lug portion, and an abutment for preventing outward movement of said bit engaging the other end of the bit.

9. In a-cutter chain, a chain block having a socket, a bit holder 'receivable in said block socket and having a socket for receiving a cutter bit, a double-pointed reversible cutter bit receivable in said `holder socket, means cooperating with said holder and adjustable relative to said block to press the inner end of said holder rearwardly and to move said holder relative to said block to move the mouth of said bit receiving socket transversely to the path of chain travel, and means stationary with respect to said block (luring such holder movement relative to said block andproviding a surface engageable with the outer end of r said bit for imparting an endwise clamping pressure to the bit as said holder is so moved relative 4to said block by said cooperating holder moving means.

10. In a cutter chain, a chain block having a socket to receive a bit holder, abit having cutting points at its opposite ends at the relatively remote extremities of plane cutting faces disposed in the sides of an obtuse dihedral angle, and means for supporting said bit and clamping the same under longitudinal compression rigidly relative to said chain block, said bit clamping same approximate cross section as said bit and further having-abutment means extending trans.. versely with respect'to said opening to limit bit motion in one direction within said opening, and a surface in stationary relation to -said chain block and relative to which, while said surface remains in such stationary relation, said bit holder is movable upon insertion thereof in said socket and into contact with which said bit is brought by such inserting movement of said bit holder, said bi t holder at the end thereof which enters said socket approximating in front to back dimension the dimension of said socket from front toback.

11. In a device of the class described, a chain block having a socket, a bit holder having a porried by said block'providing an abutment disposed forward ,of said holder in terms of the direction of block movement and relative to which the portion of said holder which is receivedin said block socket is slidable in a direction longitudinally of said socket while said abutment-providing means remains in its normal operative relation with respect to the block, a bit received in said holder and having a portion projecting angularly forwardly therefrom in the direction ofv block movement, and means carried by said chain block and coacting directly with said bit holder and exerting a rearward pressure thereon to move the same to force the projecting portion of said bit into contact with said abutment.

12. In a cutter chain, in combination, a cutting element having at its opposite ends plane surfaces disposed in the sides of an obtuse dihesaid cutting elementand concurrently engaging both of the same and cooperating with said passage in holding said cutting element immovable with respect to its moving means, one of said two means last mentioned movable, during the positioning `of said cutting element as aforesaid, with said means which provides a cutting element receiving passage and'relative to the other of said two means to apply pressure to said cutting element longitudinally of the latter, and

means for exerting a rearwardly acting force directly on said cutting element receiving passage providing member to cause the same to effect the application of pressure to said cutting element longitudinally of the latter.

13. In a cutter chain, in combination, a cuttersupporting chain block, a double-ended bit provided with cutting surfaces at its opposite ends each symmetrical with respect both to major and minor axes and respectively lying in the sides of an obtuse dihedral angle, and means for clamping and supporting said bit upon said block including al bit holder having a supporting portion receivable within said block and a head through' which a downwardly rearwardly inclined bitreceiving opening extends, an abutment element on the` block having an abutment surface engageable, in the inward position of said holder, with partial movement of withdrawal of said bit holdtion receivable within said socket, means carceiving passage, and means respectively contactl ing the forward and rearward plane surfaces of er relative to said block, and means coacting with said supporting portion of said holder at a point nearer the base of the block than any portion of said abutment element, for securing said holder in the block.

A 1&1;y Ina-cutter chain, in combination, a cutter bit having `opposingly diagonally cut ends providingfcuttin'g points at the same side of the bit,

a "cutter supporting bit block, and means for securing saidpbit upon said block including a bit holder having a supporting portion receivable within saidgbloick and a head portion traversed by a downwardlyrearwardly inclined bit receiving opening,I and an abutment on said block and relative towhich said holder is bodily longitudinally movable, while said abutment remains stationary, as the supporting portion of the holder is moved inwardly Within said block, said abutment providing an inclined surface facing rearwardly of said block and engageable with an inactive portion of the active cutting end of the bit.

15. In combination, a cutter bit having when in use a forward cutting face, a rearward surface whose elements make acute angles with the cutting face, and an inward surface disposed at substantial angles, one of which is obtuse, with respect to said cutting face and said rearward sui-- face respectively and itself constituting a usable cutting face, the cutting faces of said bit being elongated and symmetrical with respect both to their major and minor axes, and means for supporting said -bit and moving the same during cutting including a chain block having an opening to receive a bit holder and a removable bit holder traversed by an opening having a surface inclined forwardly and outwardly'with respect to .a tangent to the path of travel of the bit supporting and moving means, said last mentioned surface engageable by said rearward bit surface' and supporting the bit with its cutting face forwardly inclined, said bit supporting and moving means providing further an abutment engageable by the inactive cutting face of the bit and precludng inward movement of the latter, and said bit supporting and moving means still furtherincluding an abutment element relative to which said bit holder is bodily movable upon inward movement thereof within said block opening while said abutment element is stationary with respect to the block and which abutment element provides a surface engageable with the active cutting face of the bit inwardly of the outermost end of the latter and cooperating with said abutment in securing the bit in cutting position.

opening and having its forward diagonally cut end abutting against said abutment surface when said holder shank is pressed inwardly in said socket, said abutment surface of such height and said bit holder shank of such length, and said abutment surface and socket so positioned relative to each other, and said bit of such cross sectional dimension that said opening can be positioned to enable said bit to be forwardly withdrawn from said opening merely by partial withdrawal of said shank from said socket and concurrent outward movement of said opening relative to said abutment surface, means for supporting the inactive diagonally cut end of said bit, and means coacting with the holder shank to cause clamping of the bit under longitudinal compression with its forward diagonally cut end pressed against said abutment surface.

17. In a cutter chain, the combination comprising a chain block having a holder-receiving socket having a rear wall, said block having also a rearwardly facing, forwardly and outwardly inclined, abutment surface Vfixed against forward and inward movement with'respect thereto, a holder having a shank receivable in said block Socket and movable inwardly and outwardly relative to said block socket to change the position of the outer end of said shank relative to said inclined abutment surface, said holder also having at the outer e-nd of its shank a head provided with a forwardly and outwardly inclined bitreceiving opening extending therethrough, a double-ended reversible cutter bit having cutting faces terminating in cutting points at the opposite ends of the bit, said cutter bit receivable in said holder head opening with its active cutting face projecting forwardly and outwardly from the holder and with the inner portion of its active cutting face pressed, when said shank is moved inwardly in said socket, against said inclined abutment surface, inward movement of said holder shank within said block socket positioning said bit for clamping thereof in cutting position on the block with said inclined abutment surface holding said bit against forward release from said holder head opening, and outward movement of the holder shank within said block socket and concurrent outward movement of said head relative to said inclined abutment surface effecting release of the bit from said inclined abutment surface, and means on said block for securing the holder shank in said block socket including means for pressing the same towards the rear wall of said socket.

18. In a cutter chain, in combination, a chain block having a bit holder receiving socket therein and supporting means providing, in advance of said socket, a rearwardly facing, forwardly and outwardly inclined, abutment surface, a holder having a head provided with a forwardly and outwardly inclined bit-receiving opening extending therethrough, said holder having a shank receivable in said block socket and movable inwardly and outwardly relative to said block socket to vary the position of the said bit-receiving opening relative to said inclined abutment surface, a double ended reversible cutter bit having cutting faces terminating in cutting points at the opposite ends of the bit, said cutter bit receivable in said holder head opening with 'its-active cutting face projecting forwardly and outwardly from said holder and, when said holder shank has'been moved inwardly in said socket, with the inner portion of said active cutting face pressed against said inclined abutment surface, inward movement of the holder shank in said block socket and the concurrent movement of said head relative to said abutment surface lmoving the bit into cutting position on said block with said inclined abutment surface holding said bit against forward release from said holder head opening and outward movement of said holder shank within said block socket and concurrent outward movement of said head relative to saidl abutment surface effecting release of said bitf from said inclined abutment surface and freeing said bit for removal, and means on said block for securing the holder shank in said block socket including a set screw extending beneath said abutment surface providing means and engaging the forward sid-e of said shank.

19. In a cutter chain, in combination, a bit block having a bit holder receiving socket therein extending transversely to the length of Afthe block, a double-pointed reversible cutter bit having obliquely related cutting faces at its opposite ends, and means for clamping said bit in cutting position on said block or releasing it for removal without removing its clamping means from the block including means carried on the block providing a rearwardly facing abutment surface en- ,gageable with the active cutting face of the bit to prevent forward escape of the latter when the same is in cutting position on the block and a holder having a rearwardly inclined bit-receiving openingfpositionable upon pressing of said holder inwardly in said socket -to bring the opening -therein into a position in which said abutment surface constitutes an obstruction opposite the mouth of said opening, and means acting on said holder and exerting a force thereon tending to increase the degree of obstruction of said opening by said abutment for securing said holder in said socket and effecting clamping of said bit.

20. In combination; a chain block having a bit holder receiving socket, a bit holder having a shank received in'said socket and a head having a bit receiving opening, a bit received in said opening and having a forwardly and outwardly sloping cutting surface projecting from said head, means extending into said socket and engaging said shank to force the latter towards the rear of said socket, and an abutment engaged by the inactive inner portion of said cutting surface and having supporting means, said supporting means for said abutment disposed wholly to the outside of said first mentioned means.

21. In combination, a chain block having a bit holder receiving socket, a bit holder having a shank slidably received in said socket and a head having a bit receiving opening, a bit in said opening having a forwardly and outwardly projecting cutting face, an abutment on said block precluding forward withdrawal of the bit from said opening when said shank is in its inner position in said socket, the length of said shank being great enough to enable movement of said head outwardly sufiiciently to enable bit withdrawal over the top of said abutment while at least the end of said shank still remains in the socket, and means acting directly on said shank to press the latter rearwardly in the socket.

22. In a cutter chain, in combination, a chain block having a socket for receiving the shank of a bit holder, said socket disposed at substantially right angles to the path of travel of the cutter chain, a cutter bit holder having a head and a shank, said shank receivable in said block socket, said holder head having an outwardly and forwardly inclined opening for receiving a. cutter bit, said opening extending completely through the holder head from front to back, a doubleended reversible cutter bit having obliquely related cutting faces at its opposite ends, said cutter bit beinginsertible in said holder head opening from the front of the holder prior to the complete insertionof the holder shank withinl said block socket, said cutter bit having its active cutting face projecting forwardly and outwardly from said holder head andits inactive cutting face projecting rearwardly from said head opening at the rear side of said holder head, and means sep- 'arate from said holder andassociated with the latter and disposed at the forward side of the holder, said last mentioned means providing a rearwardly facing abutment surface engageable with the inner portion of the active cutting face of the bit to prevent forward escape of the bit from the holder opening when the holder shank is completely inserted in said block socket.

23. In a cutter chain, in combination, a chain block having a socket for receiving the shank of a bit holder, said socket disposed at substantially right angles to the path of travel of the cutter chain, a cutter bit holder havingahead and a shank, said shank receivable n'sald block socket, said holder head having an outwardly and forwardly inclined opening for receiving a cutter bit, said opening extending completely through the holder head from front to back, a double-ended reversible cutter bit having obliquelyrelated cutting faces at its opposite ends, said cutter bit being' insertible in said holder head opening from the front of the holder prior to the complete insertion of the holder shank within said block socket, said cutter bit having its active cutting face projecting forwardly and outwardly from said holder head and its inactive cutting face projecting rearwardly from said head opening at the rear side of said holder head, and means separate from said holder and associated with the latter and disposed at the forward side of the holder, said last mentioned means providing a rearwardly facing abutment surface engageable with the inner portion of the active cutting face of the bit to prevent forward escape of the bit from the holder opening when the holder shank is completely inserted in said block socket, said means for preventing forward escape of the bit from the holder having a shank portion projecting within said block socket at the forward side of said holder shank.

24. In a cutter chain, in combination, a chain block having a socket for receiving the shank of a bit holder, said socket disposed at substantially right angles to the path of travel of the cutter chain, a cutterbit holder having a head and a shank, said shank receivable in said block socket, said holder head having an outwardly and forwardly inclined opening for receiving a cutter bit, said opening extending completely through the holder head from front to back, a double-ended reversible cutter bit having obliquely related cutting faces at its opposite ends, said cutter bit being insertible in said holder head opening from the front of the holder prior to the complete insertion of the holder shank within said block socket, said cutter bit having its active cutting face projecting forwardly and outwardly from said holder head and its inactive cutting face projecting rearwardly from said head opening at the rear side of said holder head, and means separate from said holder and associated with the latter and disposed at the forward side of the holder, said last mentioned means providing a rearwardly facing abutment surface engageable with the inner portion of the active cutting face of the bit to prevent forward escape of the bit from the holder opening when the holder shank is completely inserted in said block socket, said means for preventing forward escape of the bit from the holder having Aa shank portion projecting within said block socket at the forward side of said holder shank, said holder shank being cut away at its forward side and said shank portion being received in the space so provided.

MORRIS P. HOLMES.

, CERTIFICATE 'OF CORRECTION. Patent No. 2,2L;l;,199. June 5', 19m.

' MORRIS P. HOLMES. It is hereby certified that error appears in the printed specifiction of the above numbered patent requiring correction as follows: Page 1, second column, line 2l, for "reecivirg" read -receving; page 2., second co1- umn, line 25, strike out the words "is provided which"; end that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

signed and Sealed this zpnd day of July, A. D. 19m.

- Henry Van Arsdale, (Seal) Acting Commissioner fof Patents. 

